Thousands of oil-rig workers, military personnel and aviation crews go through HUET, or "dunker," training each year to learn to survive a helicopter ditching in the ocean. Here's how it works.

They turned off the lights before the helicopter airframe hit the surface of the pool. In the dark, the churn of the water that tried to pull me from the four-point harness was the main indication that the helo's cabin was rotating. When it came to rest I was upside down in the water, strapped into a seat, eyes closed, holding my breath. There was a locked window by my shoulder. My job: Perform some minor Houdini-ism to escape the helicopter and find my way back to the surface. Then I'd breathe. And then we'd reset the equipment and do it again.

More From Popular Mechanics

Helicopter underwater escape egress training, or HUET, is commonly called dunker training in the military. Many helicopter pilots and crews, Drug Enforcement Agency personnel, Special Forces units, and offshore oil-rig workers go through similar programs each year. I enrolled in a modified version of the program called Cold-Environs HUET as a prerequisite for flying to Royal Dutch Shell's Kulluk offshore oil rig, which was working in the Beaufort Sea north of Alaska. During my four-day visit in late October to the rig, I would be learning about the future of offshore drilling in the Arctic Ocean. This HUET training was the same program that Shell requires of many of its employees and contractors. I went through the training at Survival Systems USA in Groton, Conn., a facility located a short distance from the Naval Submarine Base New London and the U.S. Coast Guard Academy.

Being dunked wasn't the scariest part of my two-day HUET training. The adrenaline really cranked up during the classroom sessions, as my classmates and I sat in a drab conference room viewing 83 PowerPoint slides and several disturbing videos. We watched as a helicopter carrying Marines crashed into the sea during a training exercise gone wrong in 1999. Seven men died. In another video a survivor of the crash described slowly groping his way to a window, encumbered by his combat gear. He eventually reached the surface, despite a broken back. Two British videos demonstrated the effects of cold water on performance: In water chilled to 50 degrees F, an Olympic swimmer was able to hold his breath for only 10 seconds. Another Olympian, this one a silver medalist, was able to breast stroke for about 7 minutes before she lost all muscle control and devolved into a slowly undulating tangle of limbs. Message received.

After lunch, we walked up some metal stairs to a pool inside what looked like a small aircraft hangar. I zipped myself tightly into a cold-water Mustang Survival suit, then added an oversize personal flotation device and, on the second day, a rebreathing apparatus, which was all equipment required by Shell. (I glanced in a mirror and thought the reflection had Apollo 11 overtones, if Buzz Aldrin had been a dork in a banana-colored Muppets costume.) My two classmates were former Army men, a test pilot and a flight engineer, who now worked for a military contractor. They wore standard flightsuits, which looked very comfortable in comparison. We practiced skills such as righting an overturned life raft and climbing into it from the water, linking arms and legs with other survivors in the water, and clearing an air-bottle regulator while hanging upside down in the pool. We also took a number of trips in the dunker.

At first, I found it easier to escape the helicopter by simply holding my breath, rather than fumbling with the breathing device. Jon Ehm, the facility's chief instructor, reminded me that it's much harder to hold your breath in frigid water—and that in the simulator I was in shallow water and uninjured. You've got to learn to use the breathing device in an emergency. According to Ehm and my classmates, U.S. helicopter crews typically carry small bottles of compressed air, good for about two minutes, that work much like standard SCUBA gear. Shell uses the Air Pocket, made by a British company called Shark Survival, that you fill with air from your own lungs in the moments before submersion. You can then rebreathe the air for a limited time. (A small canister of air built into the device helps fill the pocket.) One problem I thought I saw with the system is that you can't clear the mouthpiece underwater, an easy operation with an air-bottle regulator. And I worried that if I didn't manage to get a lungful of air before submersion, the supply would be limited. But obviously I'm no expert, and the system is used extensively in the North Sea.

By the end of the second afternoon, I thought I'd learned what Ehm was trying to teach me, and hoped to heck I'd never get to try out my new skills. The following is the complete, real-world scenario you'd be preparing for if you took the same course.

Ditching, Ditching...

You're flying out to work on one of Shell's new offshore rigs in the Arctic Ocean, and the pilot announces that the helicopter is in trouble and going down. You adopt a ditch position to protect your limbs and head as the machine hits the surface of the ocean. It's a controlled emergency landing—not a crash, which is much harder to survive. You pull open the Air Pocket, which is strapped to your chest, and insert the mouthpiece. If there's time, you apply the nose plug that's attached. As the cabin begins to fill with frigid water, you take a deep breath, click a control valve into the closed position, and breathe out into the Air Pocket.

Most of a helicopter's weight—the engine, transmission, rotors—are on top of the craft, so it tends to roll immediately and begin to sink. Flotation devices that inflate automatically when the helicopter hits the water may prevent this from happening. But in this case it does invert. You are facing danger from hypothermia and suffocation, which may be exacerbated by panic, disorientation, and darkness.

The violent rush of water tries to rip the mouthpiece out, but you clamp down on it with your teeth. When you can think again, you are strapped tightly into a seat, unsure which way is up, trying to breathe calmly through your mouth. Your feet are flat on the floor: In many helicopters the seats are designed to "stroke," or collapse on impact; if your feet had been tucked beneath the seat it could have broken your legs and trapped you. You keep your eyes closed. In all likelihood, you are in blackness anyway, and the water may be clouded with hydraulic fluid and fuel that would cause chemical burns. You'll need your eyes later, if you manage to escape the airframe and reach the surface.

Before the flight, you noted that the latch to the emergency window was positioned next to your hip. You bring your hand down to the hip, and then straight out to find the latch. Let's make it easy: The latch is still working, and the window pops off, as it's supposed to. You grasp the window frame with one hand. You don't let go. With the other hand, you undo the harness, opening the buckle and pulling it sharply toward your feet to disengage all four straps. You had to wait until this moment; if you had escaped the harness any earlier, you'd be floating through the interior of the helicopter, groping for an exit, your chances of survival drastically reduced. You now grasp the window opening with both hands, and pull yourself through. You don't know which way is up, but your Mustang Survival suit is buoyant and it pulls you toward the surface.

Since completing the HUET training, I've met several people who said they found it fun. That was humbling. But what struck me at the time was how many thousands of people fly helicopters over dangerous waters each year, and not just hardened hero types such as Navy SEALS. Those of us who use gasoline owe our lifestyles in part to crane operators, mechanics, and roughnecks who commute to work by helicopter and face some real risk to do it. This year, two helicopters ditched in the North Sea: one in May that was carrying 14 oil rig workers and another in October that carried 19 workers. (Neither helicopter rolled, and there were no serious injuries.) Such incidents are certainly rare, but I was convinced: HUET training is for real. I was going to the Arctic in a couple of weeks. And when Jon Ehm asked me to take one more ride in the dunker, I didn't argue.